Filter



Jan. 18, 1949- w. w. HALLINAN 2,459,318

FILTER 2 Sheets-Sheet 1 Filed June 10, 1946 Jan. 18, 1949. w. w. HALLlNAN 2,459,318

FILTER Filed June 10, 1946 2 Sheets-Sheet 2 [mien far; A/ZZ/zm fifZh/izm mat/k Y dizzy.

Patented 18, 1949 UNITED STATES PATENT OFFICE FILTER William w. Hallinan, Racine, Wis.

Application June 10, 1946, Serial No. 675,765

6 Claims. 1

The present invention relates 'to filters and is particularly concerned with an improved commercial form of the filter covered by my prior Patent No. 2,389,431, issued. November 20, 1945 for filters. This application is a continuation-inpart of my application for Filters, Serial No. 663,360, filed April 19, 1946.

While the present filter units are capable of general application and may be used for many different purposes, they are preferably made of such size and structure that they may be employed in oil burner systems for filtering the fuel oil preliminary to its use in burners of the nozzle or other types.

One of the objects of the invention is the provision of an improved filter unit for oil burners and other purposes, which is adapted to separate from liquids such as fuel oil, substantially all solid residue and fine matter in suspension so that there will be no tendency of the nozzle ofthe oil burners to becomefouled with small solid particles or gummy materials:

Another object of the invention is to provide a more efficient oil filter than the devices which have been employed heretofore in oil burner systems, having a greater filtering area and adapted to provide efiicient filtering action with a minimum pressure differential between the inlet and outlet of the filtering housing.

Another object of the invention is the provision of an improved filter which not only removes all solids and gummy matter from the liquid to be filtered, but which also removes all fuzz and fine fibrous or fiocculent material, thus providing a substantially clear filtrate.

Another object of the invention is the provision of an improved filter unit which is so constructed that in an emergency a service man may provide an emergency filterby improvising a few filter elements out of fabric or the like until he has had an opportunity to secure the filter elements which may be used as replacements.

Another object of the invention is the provision of an improved filter unit of the fibrous type which may be constructed at a low cost, and thrown away when dirty so that the filter may be kept in a clean and efficient condition at all times at a minimum expense.

Another object of the invention is the provision of an improved filter assembly which is provided with a safety bypass of such character that when the filter elements have become so clogged with residue that they will not pass liquid, the filter itself may be lifted from its seat to bypass the oil and to continue essential operation of the device utilizing the liquid which is being filtered.

Another object of the invention is the provision of an improved filter which requires a minimum number of parts, which is adjustable as to the pressure that may be applied to it, which may be manufactured with a minimum number of ma-.

chining operations, which is sturdy, emcient, economical and adapted to be -used a long period of time without replacement, except clean filter pads that make up the filter assembly.

Other objects and advantages of the invention will be apparent from the following description and the accompanying drawings in which similar characters of reference indicate similar parts throughout the several views.

Referring to the sheets of drawings, of which there are two,

Fig; 1 is a side elevational view of a filter unit shown in connection with a housing, the housing being in section along a plane passing through its axis;

Fig. 2 is a longitudinal sectional view of the filter unit taken on' a plane passing through its axis with the supporting rod and alignment pins in elevation;

Fig. 3 is a bottom plan view of the pad supporting partition taken on the plane 3-3 of Fig. 2 looking in the direction of the arrows;

Fig. 4 is a bottom plan view of the filter cloth, which is preferably included for the purpose of removing all fuzz or similar material which might detach itself from felt pads, from' the liquid being filtered, taken on the plane of the line 4-4 of Fig. 2 looking in the direction of the arrows;

Fig. 5 is a horizontal sectional view taken on the plane of the line 5-5 of Fig, 2 looking downwardly in the direction of the arrows showing the structure of the top plate which blocks certain passages;

Fig. 6 is a horizontal sectional view taken on the plane of the line 66 of Fig. 2 looking in the direction of the arrows showing a top plan view of one of the filter pads with the supporting rod and alignment pin in cross section;

Fig. 7 is a horizontal sectional view taken on the plane of the line 1-1 of Fig. 2 looking in the direction of the arrows showing a plan view of one of the alignment plates.

Fig. 8 is a horizontal sectional view taken on the plane of the line 8-8 of Fig. 2 looking in the direction of the arrows showing a plan view of modification in which the filter element consists of a single pad of fibrous material located between the end plates, which determine the passages into which liquid flows and the passages from which the filtrate flows;

Fig. 11 is an enlarged plan view similar to Fig. 6

showing the direction of flow of the liquid to be filtered through the filter pads to the filtrate conduits;

Fig. 12 is a view similar to Fig. 9 showing a modification of the filter unit in which two pads are interposed between each pair of alignment plates.

Referring to Fig. 1, 20 indicates in its entirety the complete filter assembly comprising a filter housing 2|, cover 22, filter unit 23 and spring 24. The housing which may be employed with the present filter unit is preferably of the type comprising one chamber of a combined straining pump and pressure regulating fuel unit.

In other embodiments of the invention the housing may be a separate one of similar structure and of suitable size as illustrated. Such a housing comprises a substantially cylindrical cast metal member, the cylindrical wall being indicated at 25. It may be provided with a side inlet opening 26 or a bottom inlet opening 21, or either one of these openings may be utilized for pressure gauges or other equipment.

The bottom opening 21 is preferably arranged in a clean-out plug 28 which is threaded into a threaded bore 29 located in the bottom of the housing so that sediment may be removed from the housing by removing the clean-out plug 28. The upper end of the housing may have a circular opening 30 surrounded by a fiat seat 3| for the cover 22, which is secured by means of a plurality of screw bolts 32 with a suitable gasket such as a cork gasket 33 interposed between the cover and housing for a liquid tight closure.

The cover 22 may also be a cast metal member having a relatively wide seating surface 34 on its lower side for engaging the housing seat 3i, and also leaving a sufificient portion of the cover seat to engage the spring 24 inside the housing.

The housing 2! is preferably formed with a pair of chambers such as the lower elongated chamber 35 of cylindrical shape for the filter pads and the upper cylindrical chamber 36 of slightly greater diameter for receiving spring 24 and the filter pad supporting member 31, which rests upon an annular shoulder 38 formed on an inwardly extending annular rib 39;

An outlet 40- is provided at one side of the'upper chamber 36 through which the filtered liquid passes to other parts of the fuel unit, such as the pump. The spring 24 comprises a loosely coiled helical spring of resilient material such as steel or spring bronze. It is of sufiicient size to have a sliding fit in the upper chamber 36, engaging the cover 22 at one end and the pad supporting member 31 at its other end to hold this pad supporting member against the annular seat 38.

The filter unit 23 may be of any of the types shown in Figs. 1 and 2, 9 or 10. The filter unit of Fig. 2 comprises the pad supporting member 31, a plurality of filter pads or elements 4! arranged in a stack and impaled upon the pins 42, 43 of a top plate 44. Additionalelements of the assembly are the pressure applying rod 45, the rigid pad aligning plates 46, end plate 41, spring 48 and threaded member 49.

The filter elements or pads which form the filter unit 23 are shown in plan in Fig. 6 in side elevation in Fig. 1. Each pad consists of a relatively thick cylindrical pad of felt, such as cotton felt, wool felt or some other suitable fibrous material provided with the outer cylindrical edge 50, the inner cylindrical bore and a plurality of through apertures for the following purposes:

Apertures 52 and 53 are for receiving the alignment pins 42 and 43, which are shown in these apertures in section in Fig. 6. Apertures 54, 55

and 56 are filtrate apertures in free communication with the outlet 46 through suitable conduits that pass through the top plate 44, as will be described in detail.

Apertures 51, 58, 59, 60 and 6| are used to receive the liquid that is to be filtered, and the walls of these apparatus constitute filtering surfaces which are in communication through the bottom plat 41 with the chamber 35 around the filter unit 23.

All of these apertures in the filter pad may be formed by punching, and the pad itself may be cut out by means of a die, thus providing a very cheap replaceable element for the filter assembly.

Referring to Fig. 8, this shows a top plan view of a bottom plate 41, and this bottom plate is preferably of the same size diameter as the filter disks, andit may be constructed of any rigid material such as thin sheets of iron or tough fibre such as indurated fibre.

The bottom plate 41 is provided with a centrally located aperture 62 for passing the pressure rod 45, shown in section in Fig. 8. Bottom plate 41 also has a plurality of apertures 63 arranged close to its center to permit the liquid to be filtered to have access to the large bore 5| in the filter pads, while still providing sufiicient material around the rod 45 to be engaged by the spring 48.

Bottom plate 41 also has all of the other apertures except the filtrate apertures 54, 55 and 56 of Fig. 6, and the bottom plate apertures are, of course, located to register with corresponding apertures in the filter pads, thus bottom plate 41 blocks off the three filtrate apertures 54, 55, 56 at the bottom and liquid has access to these filtrate apertures only after it has passed through parts of a filter pad being filtered during its passage.

The pad aligning plates 46, of which there is one between each pair of pads, may all be identical in construction and they are provided with the same apertures and are of the same size as the apertures described with respect to a filter pad in Fig. 6.

In some embodiments of the invention these alignment plates may be eliminated. They engage the upper and the lower surface of each pad of felt and by friction keep the pad aligned with therigid plates 46, which in turn are more accurately aligned with each other by means of the pins 42, 43 than can be accomplished when the pins alone are used for alignment, as illustrated in Fig. 9. V

Plates 46 accomplish no filtering action and may be made of metal such as iron or of a still fibre board such\=as indurated fibre. The top plate 44 comprises a rigid metal disk of the same size and shape as the felt pads 4|. The top plate is provided with a centrally located aperture 64 for passing the pressure rod 45, with reduced apertures 65, 66 for receiving reduced cylindrical portions of the alignment pins 42, 43 which are riveted or staked to secure them in the top plate 44. v

Top plate 44 also, has the filtrate apertures 54, 55, 56, but all of the other apertures such as the center bore 5| and the filtering apertures 516l are blocked ofi by the top plate 44. 'Thus apertures which are open at the bottom of the filter' unit are blocked off above and apertures which are open at the top of the filtering unit are blocked off below.

The pad aligning and supporting member 44 comprises the top plate 44 and the two pins 42 and 43, and a plurality of felt pads 4| and alignment plates 46 may be placed alternately one after the other on the pins 42, 43 to form a filter unit that is removable from the housing 2| and replaceable.

In orderto prevent fuzz or other fine material from the felt pads 4| from passing into the filtrate, the assembly preferably includes a filter cloth indicated at 61 which may also be of circular.

by shellac to the filter cloth. This provides a tighter joint between the filter unit and its supporting member 31, and also provides a conduit space 69 between filter cloth 81 and top plate 44. Filter cloth 61 has the centrally located aperture 64 for passing the pressure rod 45. A second annular gasket I9 surrounds the rod 45 above top plate 44 and is shellacked to the filter cloth B1 surrounding the aperture in this filter cloth. This provides a tight seal about the rod as this small gasket is engaged by the end of lug 14.

It should be noted that the filter cloth 61 has very fine mesh for the purpose of catching all fuzz and small particles that might pass the pads 4|. The pad supporting member 31 may comprise a small metal member such as a die casting consisting of a circular body or disk 18 having an axially extending lug 1| on its upper side. Lug 1| is slightly tapered to facilitate its removal from a die.

The circular body 10 of this supporting member 31 has 2. depending cylindrical rib 12, the lower edge of which (Fig. 2) engages the filter unit at the top surface of the filter cloth 81 thus filter cloth 61 and gasket 68 may be gripped or clamped between rib 12 and top plate 44. I

The cylindrical flange 12 forms an annular chamber 13 above the filter cloth 61 and below the body 10. This chamber is annular because there is a central downwardly projecting lug 14 of cylindrical shape inside the center of the chamber 13, thislug being substantially as long axially as the flange 12.

Lug 14 on the bottom of supporting member 31, body 10 and upper lug 1| are all provided with a through-bore 15 (Fig. 3) which is threaded to receive the threaded upper end of the pressure rod 45.

In order to provide a conduit leading from the annular space 13 to the upper end of bore 15. lower lug 14 and body 10 and a part of upper lug 1i are provided with slots 18 preferably regularly spaced, extending radially and axially to a point well above the upper end 11 of pressure rod 45. Thus the slots 16, one of which is seen open in Fig. 2, provide communication between the upper end of the bore 15 and the filtrate chamber 13.

The pressure rod 45 serves to secure the top plate 44 to the supporting member 31 and is provided with a nut 18 engaging the lower side of the top plate 44 and clamping gasket 88, and filter cloth 81 between flange 12 and top plate 44. Thus the complete filter unit may be removed by unscrewing the rod 45 at its upper end to take it out of the bore 15, and the pads and plates will be carried by the pins 42, 43 on plate 44.

At its lower end rod 45 preferably has a helical coil spring 48 which engages the bottom plate 41 and is itself engaged by the knurled cylindrical nut 49 located on the threaded end 19 of the rod 4 5.

. The spring 48 is relatively light, but is of sufficient strength to keep the pads and plates in close engagement with each other. The pads may become compressed when subjected to certain pressures, but upon release of the pressure they expand again, and in any event the spring 48 follows up the pads and keeps them engaging each other or engaging the intervening plates so that liquid cannot pass between the plates and pads. The spring prevents formation of cracks that would bypass dirty liquid.

The cylindrical fiange 12 on supporting mem-' ber 31 fits inside the annular rib 39 in the housing 2|, while the projecting portion of the body 10 having a lower seating surface 88 rests upon the annular flange 38 where it is held by spring 24 engaged by cover 22.

In order to further throttle the flow of liquid through the filter the upper end of the bore 15 in the supporting member 31 may be provided with a nut 8| carrying a threaded sleeve 82, and having a relatively small discharge aperture 83. Nut 8| has a sleeve 82 threaded into the upper end of bore 15.

This throttling action has been found to reduce the hum of a gear pump by increasing the suction pressure on the input side.

Referring to Fig. l, the course of the liquid to be filtered through the housing is in at the inlets 26 or '21 through the filter unit 23 out of the bore 15 and 83 into the chamber 36' and out of the outlet 48.

Referring to Fig. 11, this figure illustrates the course of the liquid to be filtered through the filter pads.

As previously described, the bottom plate 41 (Fig. 8) has apertures 516I open. Liquid to be filtered passes upwardly through these apertures and into corresponding apertures or conduits extending through all of the filter pads 4| and alignment plates 46. From these apertures in the pad assembly the liquid to be filtered passes into the walls of the pads at the apertures mentioned, and ginds its way over to the filtrate apertures 54, 55, 5

Liquid to be filtered also surrounds the unit 23 in the chamber 25 and passes into each pad at the outer cylindrical surface which becomes covered with residue. Liquid to be filtered also has access to the central bore 5i through the aperture 63 in bottom plate 41 (Fig. 8), and the liquid to be filtered passes into the pad at the inner cylindrical surface 5|, again finding its way in each case to the filtrate apertures 54, 55; 56 as illustrated by arrows in Fig. 11,

It is found that substantially all of the external surface of the pads serves as a filter surface, as well as all of the inner surface 5| of the central bore, and all of the wall surfaces of the apertures 51-6I serve as filter surfaces becoming covered with residue while still passing clear liquid.

From the holes 54, 55, 56 in the top plate 44 the filtrate passes into the chamber 13'through the slots 16 to the upper end of bore 15 and out of the small aperture 83 into chamber 36.

Referring to Fig. 9, the assembly here is exactly the same as shown in Figs. 1 and 2, except the alignment plates 46- have been omitted for pur- Referring to Fig. 10, in this embodiment one elongated cylindrical pad 84 replaces all of the pads 4| and plates 46. In this case the pins 42, 43 may be eliminated also as there are no separate pads to be kept in alignment. Such a pad 84 may be used and punched out of a felt sheet when it is to be quite short or it may be made by felting or forming the pad in a mold, which contains pins extending axially and corresponding to all of the desired apertures 5| and 52-6l.

Fig. 12 shows a modification on a reduced scale in which two pads are interposed between each pair of alignment plates, thus effecting a very good alignment with a minimum number of plates. In each of the modifications of Figs. and 12, it is again desirable to include means for aligning the holes in the pad with those of the end plates, such as pins 42, 43.

It will be apparent that should the filter pads ever become so tightly clogged that they will not pass liquid, the pressure generated in the housing 35 will force the partition ill upward against spring 24 until liquid is bypassed out of outlet 40.

The present filter units may be quickly removed and provided with new filter elements or pads, and the pads are so cheap that when they have become excessively dirtybr clogged they may be thrown away. It is not necessary, however, to throw the pads away as they can be very readily cleaned by washing them in gasoline, benzene or some other suitable solvent for the residue, and then replaced on the pins 42, 43.

As the pins require larger apertures 52, 53 in thepads and plates, and as the pins are ofiset and clamped between said cylindrical wall and said not symmetrically located on the same diameter, 1

the location of the pins permits one to assemble the pads and plates only in one way, which is the right way, with the proper apertures in alignment, not only throughout the body of the filter unit, but also at the top plate and bottom plate.

It has been found that the present filter has such a large filtering surface that it is adapted to filter a volume of liquid far in excess of that required by the usual oil burner of the nozzle type. Futhermore, the pressure difierential between the inlet and outlet of the filter may be relatively small, thus reducing the power that is absorbed in filtering.

The filter assembly may be manufactured at a very low cost and it includes a minimum number of parts, and the filter units may be used for a long period of time before it is necessary to replace them, whereas the screen devices of the prior art soon becamefdirty, requiring considerable labor-to clean them or considerably more expense to replace them.

While I have illustrated a preferred embodiment of my invention, many modifications may be made without departing from the spirit of the invention, and I do not wish to be limited to the precise details of construction set forth, but desire to avail myself of all changes Within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. A filter assembly comprising a supporting member said member comprising a disc having an axially extending lug, said lug being provided with a filter assembly outlet leading to the lower side of said disc, a centrally located rod threaded intosaid member and having a threaded member providing a retaining shoulder, a supporting plate having an aperture for said rod and engaged by said shoulder, said plate also having filtrate apertures, a lug depending from said supporting member surrounding said rod and a depending cylindrical Wall carried by said supporting member, and a filter screen having an annular gasket surrounding said rod and a second annular gasket located at the edge of said screen to be plate when the gasket surrounding said rod is clamped between said lug and said plate.

2. A filter assembly comprising a supporting member said member comprising a disc having an axially extending lug, said lug being provided with a filter assembly outlet leading to the lower side of said disc, acentrally located rod threaded into said member and having a threaded member providing a retaining shoulder, a supporting plate having an aperture for said rod and engaged by said shoulder, said plate also havin filtrate apertures, a lug depending from said supporting member surrounding said rod and a depending cylindrical wall carried by said supporting memher, and a filter screen having an annular gasket surrounding said rod and a second annular gasket located at the edge of said screen to be clamped between said cylindrical Wall and said plate when the gasket surrounding said rod is clamped between said lug and said plate, the said gasket comprising rings of cork shellacked to said screen and said screen comprising a closely woven cloth impregnated with an insoluble resin, while still presenting a fine mesh.

3. In a filter assembly, the combination of a housing having a cylindrical chamber provided between its ends with an inwardly extending annular shoulder, said chamber having an open end provided with a cover and means for securing the cover, a supporting partition having an annular seating surface to engage said annular shoulder, said housing having an outlet and having an inlet disposed on opposite sides of said partition, and resilient means above said partition engaged by said cover for holding said partition against said annular shoulder, said partition comprising a circular member provided with an axial hub having a discharge conduit through said hub, a depending annular flange on said partition, a centrally apertured screen engaging said depending fiange and provided with an annular gasket on its lower side, a metal plate engaging said gasket, said metal plate having apertures for passing liquid, a threaded rod passing through said screen and said metal plate and threaded into said hub, a complementary threaded member on said rod and clamping said plate against said said gasket, forming annular chambers above the plate and below the screen inside the gasket and above the screen and below the partition inside said annular flange.

4. In a filter assembly, the combination of a housing having a cylindrical chamber provided between its ends with an inwardly extending annular shoulder, said chamber having an open end provided with a cover and means for securing the cover, a supporting partition having an annular seating surface to engage said annular shoulder, said housing having an outlet and having an inlet disposed on opposite sides of said partition, and resilient means above said partition engaged by said cover for holding said partition against said annular shoulder, said partition comprising a circular member provided with an axial hub having a discharge conduit through said hub, a depending annular flange on said partition, a centrally apertured screen engaging said depending flange and provided with an annular gasket on its lower side, a metal plate engaging said gasket, said metal plate having apertures for passing liquid, a threaded rod passing through said screen and said metal plate and threaded into said hub, a complementary threaded memberon said rod and clamping said plate against said gasket, forming annular chambers above the plate and below the screen inside the gasket and above the screen and below the partition inside said annular flange, said gasket comprising a plurality of rings of cork shellacked to said screen, and said screen comprising a closely woven cloth impregnated with'an insoluble resin, while still presenting a fine mesh.

Ina filter assembly, the combination of a housing having a cylindrical chamber provided between its ends with an inwardly extending annular shoulder, aid chamber having an open end provided with cover and means for securing the cover, a supporting partition having an annular seating surface to engage said annular shoulder, said housing having an outlet and having an inlet disposed on opposite sides of said partition, and resilient means above said-partition engaged by said cover for holding said partition against said annular shoulder, said partition comprising a circular member provided with an axial hub having a discharge conduit th; cugh said hub, a depending annular flange on said partition, a centrally apertured screen engaging said depending flange and provided with anannular gasket on its lower side, a metal plate engaging said gasket, said metal plate having apertures for passing liquid, a threaded rod passing through said screen and said metal plate and threaded into said hub, a complementary threaded member on said rod and clamping said plate against said gasket, forming annular chambers above the plate and below the screen inside the gasket and above the screen and below the partition inside said annular flange, said. plate supporting a pair of metal pins riveted to said plate and extending parallel to said rod, a plurality of pads of felt, said pads having an enlarged central aperture surrounding said rod and having apertures for receiving said metal pins, and having inlet and filtrate apertures kept in alignment by said metal pins, said inlet and filtrate apertures serving for conducting liquid into the pads and for conducting filtrate out of the pads, said filtrate apertures registering-with the apertures in the first-mentioned plate and said inlet apertures sealed by said, first mentioned plate, and a second metal plate engagini? the last pad of felt which is remote from said partition, and having apertures for passing liquid, said inlet apertures registering with the-apertures in the second mentioned plate, and said filtrate apertures sealed by said second mentioned plate.

6. In a filter assembly, the combination of a housing having a cylindrical chamber provided between its ends with an inwardly extending an nular shoulder, said chambei'ha'vingan open end provided with a coverand' means-for securing the cover, a supporting partition having an annular seating surface to engage said annular shoulder, said housing having an outlet and having an inlet disposed on opposite sides of said partition, and resilient means above said partition engaged by said cover for holding said partition against said annular shoulder, said partition comprising a circular member provided with an axial hub having a discharge conduit through said hub, a depending annular flange on said partition, a centrally apertured screen engaging said depending fiange and provided with an annular gasket on its lower side, a metal plate engaging said gasket, said metal plate having apertures for passing liquid, a threaded rod passing through said scrcen and said metal plate and threaded into said hub, a complementary threaded member on said rod and clamping said plate against said gasket, forming, annular chambers above the plate and below the screen inside the gasket and above the screen and below the partition inside said annular flange, said plate supporting a pair of metal pins riveted to i" said plate and extending parallel to said rod, a' plurality of pads of felt, said pads having anenlarged central aperture surrounding said rod and having apertures "for'rece'iving said metal pins, and having inlet and filtrate apertures kept in alignment by said metal pins, said inlet and filtrate apertures serving for conducting liquid into the pads and for conducting filtrate out of the pads, said filtrate apertures registering with the apertures in the first-mentioned plate, and said inlet apertures sealed by said first mentioned plate, and a plurality of additional sheet metal plates located between said pads and having aligned apertures with the pads, the lowermost of said metal plates being located outside of the end pad and being engaged by c a spring on said rod, and threaded means on the end of the rod for compressing said spring and the last named plate being apertured for passing liquid, said inlet apertures registering with the apertures in saidlast named plate and said filtrate apertures being sealed by said last named plate.

WILLIAM W. HALLINAN.

REFERENCES CITED The following references are of record in the filo of this patent:

UNITED STATES PATENTS Number Name Date I 651,901 Torrance June 19, 1900 680,902 Weaver Aug. 20, 1901 1,035,248 Seavey Aug, 13,1912 1,506,967 Bosworth Sept. 2, 1924 2,186,440 Williams Jan. 9, 1940 2,196,349 West Apr. 9, 1940 2,301,120 Kamrath Nov. 3, 1942 2,331,961 Clark Oct. 19, 1943 2,332,535 Ross Oct. 26, 1943 2,389,431 Hailinan Nov. 20, 1945 FOREIGN PATENTS Number Country Date 107,090' Great Britain June 21, 1917 

